Hitherto, a variety of treating agents and coating materials have been used for the purpose of protecting substrate surfaces against various corrosive environments. Among them, coating materials capable of forming a film or capable of being cured at ambient temperature have been used widely because they need no thermal energy and hence save energy and simplify the film-forming process. Examples of such coating materials include nitrocellulose type and other clear lacquers, polyurethane type, epoxy type and other two-pack cold setting coating materials, alkyd type, polybutadiene type and other air-drying coating materials, and silicone type and other moisture-curing coating materials.
However, coating materials capable of forming a film or capable of being cured at ambient temperature are generally disadvantageous in the following points.
Clear lacquers which can form a film by mere vaporization of a solvent are inferior in the strength of the coating film and the rustproofing performance, though they give a film of glossy appearance. Two-pack type cold setting coating materials are disadvantageous in that the work for compounding the curing agent requires troublesome procedures of weighing and blending and the blended composition is inferior in workability because of their short pot life, though they give a strong coating film of high adhesive property. Air drying type coating materials are disadvantageous in that the residual unsaturated bonds may inhibit the resistance of the coating film to oxidation and weather, though they can form a coating film which is excellent in water resistance. Silicone type moisture-curing coating materials are inferior in storage stability and rustproofing performance of the coating film, though they are excellent in heat resistance and weather resistance.
Previously in U.S. Pat. No. 4,642,011, the present inventors proposed a metal-rustproofing composition which can be cured at ambient temperature and can exhibit an excellent rustproofing property even in a much smaller thickness of the coating film than those of the usual coating films. However, this composition had a problem that deterioration of product quality, such as an increase in viscosity and formation of insoluble precipitates, can occur when the composition is stored for a long period of time.
Epoxy coating materials using an amine type curing agent are rapidly cured at ambient temperature or low temperatures to form a strong coating film which exhibits an excellent adhesion to metals and a high rustproofing performance, so that they are widely used in various industries.
However, these epoxy-amine type coating materials are two-pack type coating materials and their workability is highly restricted by the troublesome weighing and blending procedures necessary for compounding the curing agent into the resin, as well as by the shortness of pot life. Further, when they are applied to nonmetallic substrates, they do not adhere well, which also limits their applicability. With the aim of solving these problems and attaining adhesion to a wide variety of materials, there have been published various publications, for example, Japanese Patent Application Kokai (Laid-Open) No. 101,100/76, which discloses compounding a compound having acryloyl groups or methacryloyl groups (hereinafter, generically referred to as (meth)acryloyl groups) to improve not only adhesion but also waterproofing adhesion and flexibility and to make the composition applicable to non-metallic substrates such as plastics.
However, such compositions are still two-pack type compositions, so that the laboriousness in procedure is not essentially overcome by these techniques.
The present inventors conducted many studies with the aim of solving the above-mentioned problems of prior coating compositions that they are applicable only to limited kinds of substrates and that they are remarkably limited in workability, and obtaining a composition which is excellent in storage stability and capable of forming a cured coating film excellent in corrosion resistance at ambient temperature or by a mild heat treatment.